XRISM high-resolution X-ray spectroscopy of Cygnus X-1: Orbital and short-term variability of iron absorption

Abstract We present the first high-resolution spectroscopy of the black hole high-mass X-ray binary Cygnus X-1 with XRISM, including orbital-phase-resolved analyses and tentative evidence of short-term variability in the Fe K band on second timescales. Using data from the Performance Verification phase in 2024 April, we analyzed spectral variability across orbital phases with the Resolve microcalorimeter and the Xtend CCD imager. The unprecedented resolution of Resolve reveals variability in highly ionized Fe absorption lines. The absorption features show orbital-phase-dependent variability in column density, ionization state, and blueshifted velocity, suggesting structural variations in the focused stellar wind along the line of sight. We also find indications of subtle broadening of the neutral Fe emission profile. In addition, intensity-sorted spectroscopy during dip phases suggests possible variability on timescales of a few seconds in the absorption features, consistent with cooler, denser, and lower-ionized gas clumps. Although the statistical significance is limited, these results hint that the stellar wind and the X-rays from the accretion disk around the black hole may interact on timescales as short as a few seconds. These XRISM results constrain wind-fed accretion in Cyg X-1 and highlight Resolve’s capability to probe plasma environments in high-mass X-ray binaries.

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Journal
Publications of the Astronomical Society of Japan
Published
2026-04-26
DOI
https://doi.org/10.1093/pasj/psag039
Primary Topic
Astrophysical Phenomena and Observations
Type
article
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0.00

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article

XRISM high-resolution X-ray spectroscopy of Cygnus X-1: Orbital and short-term variability of iron absorption

S Kobayashi, Misaki Mizumoto, Yuusuke Uchida, Kaito Ninoyu et al.
Publications of the Astronomical Society of Japan
Astrophysical Phenomena and Observations
article

XRISM high-resolution X-ray spectroscopy of Cygnus X-1: Orbital and short-term variability of iron absorption

S Kobayashi, Misaki Mizumoto, Yuusuke Uchida, Kaito Ninoyu, Jack Miller, Paul Draghis, Seoru Ito, Oluwashina Adegoke, Takayoshi Kohmura, Javier A Garcia, Tsunefumi Mizuno, Elisa Costantini, Kazutaka Yamaoka, Shinya Yamada, Ryota Tomaru, Aya Kubota, Edmund Hodges-Kluck, Natalie Hell, Hiromitsu Takahashi, Shunji Kitamoto, Ken Ebisawa, Sixuan Zhang
article en

Abstract

Abstract We present the first high-resolution spectroscopy of the black hole high-mass X-ray binary Cygnus X-1 with XRISM, including orbital-phase-resolved analyses and tentative evidence of short-term variability in the Fe K band on second timescales. Using data from the Performance Verification phase in 2024 April, we analyzed spectral variability across orbital phases with the Resolve microcalorimeter and the Xtend CCD imager. The unprecedented resolution of Resolve reveals variability in highly ionized Fe absorption lines. The absorption features show orbital-phase-dependent variability in column density, ionization state, and blueshifted velocity, suggesting structural variations in the focused stellar wind along the line of sight. We also find indications of subtle broadening of the neutral Fe emission profile. In addition, intensity-sorted spectroscopy during dip phases suggests possible variability on timescales of a few seconds in the absorption features, consistent with cooler, denser, and lower-ionized gas clumps. Although the statistical significance is limited, these results hint that the stellar wind and the X-rays from the accretion disk around the black hole may interact on timescales as short as a few seconds. These XRISM results constrain wind-fed accretion in Cyg X-1 and highlight Resolve’s capability to probe plasma environments in high-mass X-ray binaries.

Publications of the Astronomical Society of Japan
Hiroshima University (JP), California Institute of Technology (US), Lawrence Livermore National Laboratory (US), Goddard Space Flight Center (US), Rikkyo University (JP), Tokyo University of Science (JP), Shibaura Institute of Technology (JP), University of Michigan (US), University of Teacher Education Fukuoka (JP), Japan Aerospace Exploration Agency (JP), Institute of Space and Astronautical Science (JP), Space Research Organisation Netherlands (NL), Nagoya University (JP), Massachusetts Institute of Technology (US), The University of Osaka (JP)
Yamada Science Foundation, U.S. Department of Energy, Japan Society for the Promotion of Science
Openalex Percentile: Top 12%
Astrophysical Phenomena and Observations
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